Although osteoarthritis (OA) is the most common chronic joint condition and is an important public health concern among the elderly, there is a paucity of epidemiological data on risk factors for OA. This research will 1) examine whether risk factors for OA and disc degeneration (DD) vary by joint site, by single versus multiple joint involvement, and by symptomatic versus asymptomatic status across joint sites; and, 2) examine the importance of specific mechanical and metabolic risk factors for joint-specific OA and DD. Data for adults aged 50 and older from three national surveys will be analyzed: Health Examination Survey I, 1960-1962 (HES I)(n=3783); National Health and Nutrition Examination Survey I, 1971-1974 (NHANES I)(n=3373); National health and Nutrition Examination Survey II, 1976-1980 (NHANES II)(n=5108). OA status will be based on x-rays of hands and feet (HES I), knees and hips (NHANES I) and DD on cervical and lumbar spine x-rays (NHANES II). The risk factors to be analyzed for all joint sites are: age, sex, race, occupation, height, weight, skinfolds, muscularity, anthropometric girth measurements, serum cholesterol, blood pressure, diabetes, and reproductive history. Additional risk factors available for some but not all joints will also be analyzed: injury, physical activity/exercise, waist/hip ratio, triglyceride, HDL, uric acid, bone density, glucose tolerance, and leg length. Nineteen major hypotheses will be tested by multiple binomial and polychotomous logistic regression. This study offers several advantages over previous cross-sectional studies: 1) large heterogeneous samples allowing for multivariate analysis of risk factors for a variety of joints; 2) generalizability of results to the U.S. adult population; 3) respondent, clinical, and radiographic data all in the same study; and, 4) radiographic data on multiple joints that were read independent of respondent characteristics, and graded according to standard diagnostic criteria.